| 1 | # Access WeakSet through the weakref module.
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| 2 | # This code is separated-out because it is needed
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| 3 | # by abc.py to load everything else at startup.
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| 4 |
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| 5 | from _weakref import ref
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| 6 |
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| 7 | __all__ = ['WeakSet']
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| 8 |
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| 9 |
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| 10 | class _IterationGuard(object):
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| 11 | # This context manager registers itself in the current iterators of the
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| 12 | # weak container, such as to delay all removals until the context manager
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| 13 | # exits.
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| 14 | # This technique should be relatively thread-safe (since sets are).
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| 15 |
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| 16 | def __init__(self, weakcontainer):
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| 17 | # Don't create cycles
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| 18 | self.weakcontainer = ref(weakcontainer)
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| 19 |
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| 20 | def __enter__(self):
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| 21 | w = self.weakcontainer()
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| 22 | if w is not None:
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| 23 | w._iterating.add(self)
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| 24 | return self
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| 25 |
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| 26 | def __exit__(self, e, t, b):
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| 27 | w = self.weakcontainer()
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| 28 | if w is not None:
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| 29 | s = w._iterating
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| 30 | s.remove(self)
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| 31 | if not s:
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| 32 | w._commit_removals()
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| 33 |
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| 34 |
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| 35 | class WeakSet(object):
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| 36 | def __init__(self, data=None):
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| 37 | self.data = set()
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| 38 | def _remove(item, selfref=ref(self)):
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| 39 | self = selfref()
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| 40 | if self is not None:
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| 41 | if self._iterating:
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| 42 | self._pending_removals.append(item)
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| 43 | else:
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| 44 | self.data.discard(item)
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| 45 | self._remove = _remove
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| 46 | # A list of keys to be removed
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| 47 | self._pending_removals = []
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| 48 | self._iterating = set()
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| 49 | if data is not None:
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| 50 | self.update(data)
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| 51 |
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| 52 | def _commit_removals(self):
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| 53 | l = self._pending_removals
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| 54 | discard = self.data.discard
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| 55 | while l:
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| 56 | discard(l.pop())
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| 57 |
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| 58 | def __iter__(self):
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| 59 | with _IterationGuard(self):
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| 60 | for itemref in self.data:
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| 61 | item = itemref()
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| 62 | if item is not None:
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| 63 | # Caveat: the iterator will keep a strong reference to
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| 64 | # `item` until it is resumed or closed.
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| 65 | yield item
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| 66 |
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| 67 | def __len__(self):
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| 68 | return len(self.data) - len(self._pending_removals)
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| 69 |
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| 70 | def __contains__(self, item):
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| 71 | try:
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| 72 | wr = ref(item)
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| 73 | except TypeError:
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| 74 | return False
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| 75 | return wr in self.data
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| 76 |
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| 77 | def __reduce__(self):
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| 78 | return (self.__class__, (list(self),),
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| 79 | getattr(self, '__dict__', None))
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| 80 |
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| 81 | __hash__ = None
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| 82 |
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| 83 | def add(self, item):
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| 84 | if self._pending_removals:
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| 85 | self._commit_removals()
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| 86 | self.data.add(ref(item, self._remove))
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| 87 |
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| 88 | def clear(self):
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| 89 | if self._pending_removals:
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| 90 | self._commit_removals()
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| 91 | self.data.clear()
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| 92 |
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| 93 | def copy(self):
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| 94 | return self.__class__(self)
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| 95 |
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| 96 | def pop(self):
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| 97 | if self._pending_removals:
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| 98 | self._commit_removals()
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| 99 | while True:
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| 100 | try:
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| 101 | itemref = self.data.pop()
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| 102 | except KeyError:
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| 103 | raise KeyError('pop from empty WeakSet')
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| 104 | item = itemref()
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| 105 | if item is not None:
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| 106 | return item
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| 107 |
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| 108 | def remove(self, item):
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| 109 | if self._pending_removals:
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| 110 | self._commit_removals()
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| 111 | self.data.remove(ref(item))
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| 112 |
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| 113 | def discard(self, item):
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| 114 | if self._pending_removals:
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| 115 | self._commit_removals()
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| 116 | self.data.discard(ref(item))
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| 117 |
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| 118 | def update(self, other):
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| 119 | if self._pending_removals:
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| 120 | self._commit_removals()
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| 121 | for element in other:
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| 122 | self.add(element)
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| 123 |
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| 124 | def __ior__(self, other):
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| 125 | self.update(other)
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| 126 | return self
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| 127 |
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| 128 | def difference(self, other):
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| 129 | newset = self.copy()
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| 130 | newset.difference_update(other)
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| 131 | return newset
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| 132 | __sub__ = difference
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| 133 |
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| 134 | def difference_update(self, other):
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| 135 | self.__isub__(other)
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| 136 | def __isub__(self, other):
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| 137 | if self._pending_removals:
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| 138 | self._commit_removals()
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| 139 | if self is other:
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| 140 | self.data.clear()
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| 141 | else:
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| 142 | self.data.difference_update(ref(item) for item in other)
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| 143 | return self
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| 144 |
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| 145 | def intersection(self, other):
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| 146 | return self.__class__(item for item in other if item in self)
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| 147 | __and__ = intersection
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| 148 |
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| 149 | def intersection_update(self, other):
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| 150 | self.__iand__(other)
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| 151 | def __iand__(self, other):
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| 152 | if self._pending_removals:
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| 153 | self._commit_removals()
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| 154 | self.data.intersection_update(ref(item) for item in other)
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| 155 | return self
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| 156 |
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| 157 | def issubset(self, other):
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| 158 | return self.data.issubset(ref(item) for item in other)
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| 159 | __le__ = issubset
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| 160 |
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| 161 | def __lt__(self, other):
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| 162 | return self.data < set(ref(item) for item in other)
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| 163 |
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| 164 | def issuperset(self, other):
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| 165 | return self.data.issuperset(ref(item) for item in other)
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| 166 | __ge__ = issuperset
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| 167 |
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| 168 | def __gt__(self, other):
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| 169 | return self.data > set(ref(item) for item in other)
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| 170 |
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| 171 | def __eq__(self, other):
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| 172 | if not isinstance(other, self.__class__):
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| 173 | return NotImplemented
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| 174 | return self.data == set(ref(item) for item in other)
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| 175 |
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| 176 | def __ne__(self, other):
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| 177 | opposite = self.__eq__(other)
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| 178 | if opposite is NotImplemented:
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| 179 | return NotImplemented
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| 180 | return not opposite
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| 181 |
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| 182 | def symmetric_difference(self, other):
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| 183 | newset = self.copy()
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| 184 | newset.symmetric_difference_update(other)
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| 185 | return newset
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| 186 | __xor__ = symmetric_difference
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| 187 |
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| 188 | def symmetric_difference_update(self, other):
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| 189 | self.__ixor__(other)
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| 190 | def __ixor__(self, other):
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| 191 | if self._pending_removals:
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| 192 | self._commit_removals()
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| 193 | if self is other:
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| 194 | self.data.clear()
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| 195 | else:
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| 196 | self.data.symmetric_difference_update(ref(item, self._remove) for item in other)
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| 197 | return self
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| 198 |
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| 199 | def union(self, other):
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| 200 | return self.__class__(e for s in (self, other) for e in s)
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| 201 | __or__ = union
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| 202 |
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| 203 | def isdisjoint(self, other):
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| 204 | return len(self.intersection(other)) == 0
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